Distribution of broadband signals, such a video signals representing television or the like video programs, has been accomplished in a number of different ways with varying degrees of success. Some problems which still generally remain include those typical of cable television in which a relatively large number of different program channel signals are all distributed to every subscriber in analog form--a substantial use of transmission bandwidth to a location that can use only a very small fraction of the available programming at any given time. Another problem is that the customers who are most remote from the signal source may receive a significantly weaker signal than do those who are closer. A poorer quality video picture results. Also linear modems and repeaters of sufficient bandwidth to operate well in such a system are enormously expensive. Furthermore, the arrangement is relatively inflexible, as it is difficult to change features provided by the service. Some examples of different video signal distribution efforts are noted below.
An E. M. Ulicki U.S. Pat. No. 3,757,225 shows a communication system which collects analog television signals and frequency division multiplexes them onto a cable system with command control signals for distribution to a customer station where different programs may be selectively displayed on a common display channel.
In an A. E. Cutler U.S. Pat. No. 4,135,202, analog full optical fiber distribution is accomplished for several program channels. In one embodiment, program selection devices are provided in an intermediate program exchange which employs optical selection devices to enable a program signal to be steered to an individual customer.
A video and data distribution module with a customer terminal, in an I. Gimple et al. U.S. Pat. No. 4,430.731, frequency division multiplexes analog program signals with digital data ard control signals onto a transmission circuit to remote video data distribution modules in different neighborhoods. There a selected program is frequency converted to a range which is appropriate for a particular customer.
In the German patent application disclosure document No. 25,38,638, there is shown a digital distribution system for video program signals. A program signal stream is coupled through a switch matrix, in the same office with switch matrices for the voice and video parts of video telephone service, to a particular customer over an optical fiber link. The method for communicating customer selections to the switch is not specifically shown.
A T. W. Canning U.S. Pat. No. 3,992,686 teaches a backplane transmission line system for distributing signals among printed circuit boards. Components on one circuit board are interconnected to other circuit boards by way of transmission lines terminated at both ends with the characteristic impedance.
In an R. P. Gabriel paper "Dial a Program--an HF Remote Selection Cable Television System," Proceedings of The IEEE, Vol. 58, No. 7, July 1970, pages 1016-1023, there is shown another analog signal distribution system with a program exchange employing stepping switches responsive to dialing signals from a customer to direct a particular program signal to that customer.
An example of a video telephone type of switching system is shown in an R. J. Stapleton U.S. Pat. No. 3,701,849 wherein wideband signals are communicated between individual customers by way of a switching office.